[RELEASE-4.7.0] update docker file

Descriptions of the changes in this PR:

update the release version from 4.6.0 to 4.7.0 and its corresponding gpg key

Author: Sijie Guo <[email protected]>

Reviewers: Enrico Olivelli <[email protected]>

This closes apache#1351 from sijie/update_docker_file

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